Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the burden of behavioral disclosure. It does disclose an authorization requirement (the key from claim_mailbox) and the scoped address, but it does not state whether reading consumes/destroys mail, what the return payload looks like, or how errors are handled. The verb 'Read' implies non-destructive retrieval, but important behavior is left undefined.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences with no filler. The action and resource are front-loaded, and the critical prerequisite is stated immediately, making it easy for an agent to parse quickly.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple two-parameter read operation, the description covers the action, the scoping condition, and the required key. It does not describe the return format or error behavior, and since there is no output schema this is a minor gap, but 'read mail' provides a reasonable expectation that mail content is returned.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Even though schema description coverage is 0%, the description gives meaningful context for both parameters: the key's provenance is specified as coming from claim_mailbox, and 'the address you claimed' effectively maps to the handle. It would be clearer if it explicitly named the handle parameter, but both parameters receive usable meaning.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb-resource pair ('Read mail') and narrows it to 'the address you claimed,' which distinguishes it from unrelated operations. It does not explicitly name sibling tools like read_inbox or read_refuge, so differentiation is implicit rather than explicit.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides a clear precondition: the tool should be used only after claiming an address and only with the key obtained from claim_mailbox. This gives solid situational context, but it does not state when not to use the tool or explicitly compare it with alternative read tools.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.